The present invention is generally in the field of irrigation and more specifically it is concerned with a method and system for irrigation by condensation.
There is always a demand for fresh irrigation of water and there occurs particular problems in remote country areas which lack sufficient resources of fresh water and where supply and water by pipes is costly owing to extreme distances requiring substantially long pipes and power supplies for pumping stations etc.
Various solutions are provided for that purpose, such as desalination of sea water, capturing flood water, exploiting underground aquifers etc. However, these methods of supplying irrigation water have one or more of several drawbacks such as providing water at poor quality not suitable for agriculture, high cost and low efficiency, high wear of equipment, dependency upon precipitation, etc.
Other arrangements provide recovering moisture from air masses, typically by various condensation methods. These arrangements are usually highly costly and of questionable efficiency. Some particular examples provide limited solutions adjacent coastal zones wherein deep ocean water at significantly low temperature may be pumped for recovering of fresh water by condensation.
Some of the prior art patents concerning recovering of fresh water from the moist in the air are the following U.S. Pat. Nos. 661,944, 3,498,077, 3,675,442 and 4,459,177.
U.S. Pat. Nos. 1,442,367, 3,890,740, 4,577,435 and 6,148,559 are all concerned with prebudding control methods and apparatuses which achieve such control by governing the temperature of the agricultural growth.
It is an object of the present invention to provide an irrigation system for recovering water from moisture contained in the soil or air by condensation over pipes buried in the soil at a depth corresponding with depths of roots of agriculture growth or laid on the ground. The term xe2x80x9cadjacent ground surfacexe2x80x9d will be used to denote laying the piping system either or both upon the ground surface or below ground surface, as denoted above.
The term underground is used to denote that the piping is received within any media suitable for agriculture growth, wherein the pipes are received within said media. In case of an artificial soil bedding this term may be understood also as in-ground, depending on the context. Herein the specification and claims, the terms ground and soil are interchangeably used to denote the growing media.
According to a first aspect of the present invention there is provided an irrigation system comprising an energized cooling system for cooling a liquid to a temperature below ground temperature, closed-loop placed on or adjacent below ground surface and an energized liquid circulating arrangement for circulating the liquid through the system, whereby propelling the cooled liquid through the piping extracts moisture from the environment (air and soil) by condensation over the piping, for consumption by agriculture growth in the vicinity of the piping. By an embodiment of the invention, substantial portions of the piping may be laid on the ground.
The term closed-loop denoted a system wherein substantially there is no loss of liquid to the environment.
In order to increase overall thermal efficiency, one or more components of the system are buried under ground for reducing heat loss during hot hours of the day. In some cases it might be advantageous to provide additional cooling systems for increasing performances of the system.
Typically, the cooling system includes heat exchanger arrangements for cooling the liquid.
The system can be a so-called stand alone irrigation system, or it may be used as a co-existing system along with a conventional irrigation system, where each of the systems may be selectively used.
The liquid circulating arrangement and the cooling system may be energized by a variety of energy sources such as, solar energy supply, wind energy, electric energy (main supply, generators, etc,), hydraulic energy, biomass energy and source of natural cold water.
In order to increase the amount of liquid recovered by condensation, the piping may be inert with increased section area as compared with a pipe having a circular cross-section. This is possible by forming the piping with indentations or serrated sheath surface, increasing the effective surface of the piping which is in contact with the ground.
Typically, a control system is provided for retaining a substantially constant xcex94T by regulating liquid temperature where:
xcex94T=Tgxe2x88x92T1
Tg =ground temperature measure at the vicinity of the piping;
T1=liquid temperature running through the piping, and where T1 greater than 0.
The control system is utilized also for governing flow parameters and operative patterns of the irrigation system, e.g. sensing the humidity of the soil or ambient air at different hours of the day in order to recover maximum condensation liquid, determining hours of the day during which the liquids in the system is at its minimal temperature, etc.
In accordance with a second aspect of, the present invention there is provided a method for underground irrigation according to which a liquid is propelled at a temperature below ground temperature, through a closed piping system buried below ground surface, thereby condensing liquid over the piping sheath for consumption by agriculture growth in the vicinity of the piping.
In accordance with the irrigation method of the invention, the piping is connected to a liquid reservoir, a circulating arrangement and a cooling system for chilling the liquid.
In accordance with another aspect of the invention the irrigation system comprises an irrigation system comprising a closed-loop piping system of which at least a portion of which is a condensing section extending on or adjacent below ground surface, and at least another portion of which is a cool-collecting section buried under ground at a cool ground zone; said closed-loop piping holding a liquid which is propelled by a circulating system fitted along the piping system; whereby said liquid is chilled by heat exchanging at the cool ground zone and then flows to the condensing section where moisture from the vicinity is extracted by condensation over condensing section readily available for consumption by agriculture growth.
The term xe2x80x9ccool ground zonexe2x80x9d as used herein in the specification refers to a level under ground wherein the mean soil temperature remains essentially constant in spite decrease in depth This zone is at a depth at which temperature differences are minor. The arrangement in accordance with this application is such that the liquid at the cool-collecting section is chilled by the soil which is significantly cooler than ambient air temperature and as the chilled liquid reaches the condensing section, it causes condensation over sheets of the piping at the condensing section, extracting moisture from the environment which is then to be consumed by the growth.
Where the ambient relative humidity is low, a cooling system may be incorporated with the irrigation system, to thereby reduce the temperature of the liquid within the piping for improving condensation performances.
Typically there is provided a control system in association with the irrigation system for determining the due point temperature which is the temperature at which the chilled liquid flowing within the condensing section must reach and the ambient temperature surrounding the condensing section, for moisture to form on sheets of the piping.
The liquid flowing through the piping is at essentially constant pressure.
An irrigation system in accordance with an embodiment of the invention is arranged such that the piping system comprises several condensing sections and several cool-collecting sections; said cool-collecting sections being arranged in altering depths to thereby minimize heat transfer influence between adjoining sections.